Here’s what a real Washington scandal looks like: Many Union soldiers wounded at Bull Run, the Civil War’s first major battle, had to walk some 20 miles to the nation’s capital in search of medical care. Hundreds too badly hurt remained behind, some for as long as a week, until they were carried off and treated.

Hardly any thought had been given to tending to wounded troops. More than 1,500 soldiers seeking treatment overwhelmed Washington’s four hospitals as well as an inexperienced military medical corps. President Abraham Lincoln was among those who watched bloodied soldiers walk the streets in search of shelter. Newspaper accounts of their plight enraged Americans.

The military debacle in Northern Virginia in July 1861 revealed more than a fundamentally flawed and unprepared Union army, historian Scott McGaugh writes. “Its medical department needed new leadership, organization, resources, and perhaps most importantly, the authority to adequately prepare, deploy and treat the wounded in battle.”

Central to the life-saving changes that followed was a military doctor who had spent more than a decade in army outposts around the country. Jonathan Letterman, a native of Canonsburg, Pa., educated at Philadelphia’s Jefferson Medical College, knew all too well how commanders and the military bureaucracy could treat doctors with disdain and ignore their advice about hygiene and nutrition.

In “Surgeon in Blue: Jonathan Letterman, the Civil War Doctor Who Pioneered Battlefield Care,” McGaugh blends the doctor’s personal history with an examination of medical practices of the era and an overview of key Civil War battles. McGaugh provides telling details within a concise narrative to give Letterman’s personal story the context necessary for appreciating his influence.

Bull Run did not convince all military officers that planning for the care of casualties should be part of overall battle strategy. As important to Letterman in changing perceptions was the new surgeon general, William Hammond, who had an ally to the new top Union commander, Gen. George B. McClellan. Hammond respected Letterman’s organizational skills and gave him greater and greater responsibility for determining how to anticipate and meet the needs of wounded troops.

By the time Union and Confederate forces clashed in September 1862 at Antietam Creek near Sharpsburg, Md., Letterman’s reforms were taking hold. Illness among troops had fallen after weekly baths were ordered, for example, and cases of scurvy began to recede once fresh vegetables were routinely provided. The construction and maintenance of latrines were given more attention. Another key change: Officers were being held accountable for the health of their men.

Antietam provided evidence of the effectiveness of Letterman’s new ambulance system and the pre-battle planning in which he organized a network of hospitals using barns, farmhouses and other suitable structures. He needed those facilities: By some estimates, 21,000 or more soldiers in blue or gray were killed or wounded.

What lay ahead for Letterman? Fredericksburg, Chancellorsville and Gettysburg — and more bureaucratic infighting. By following Letterman from one bloody battle to another, McGaugh’s well-researched book adds a sobering tone to the 150th anniversary of a conflict that advanced medical care at a terrible cost.